As is well known, optical systems are used in many environments in order to focus light. Many optical systems include imperfections which can introduce distortions or aberrations into the focusing of the light which reduces resolution and image quality. This occurs not only in mechanical systems which include manufactured lenses made from glass and other materials, but also in biological specimens such as the human eye. The present invention has particular application to compensating for aberrations caused by imperfections of the “lensing system” of a human eye comprising the cornea and eye lens, and in particular to a fundus camera including such an apparatus which can be used to take images of the fundus of a human eye for diagnosis and treatment purposes.
Fundus cameras are known and are used to examine the fundus or back of a person's eye. In general, the fundus camera comprises a microscope and a camera. The camera directs a beam of light into a person's eye and light reflected from the fundus is captured so that an image of the fundus can be obtained. The resolution of the image of the fundus is limited by the optical quality of the person's eye and, in particular, by distortions or aberrations which may be introduced by virtue of the light passing through the cornea and lens of the eye. In one known fundus camera, light from a person's eye is reflected by a deformable mirror to a charge coupled device for producing an image of the fundus. The charge coupled device is connected to a processor which in turn manipulates the deformable mirror to compensate for distortions which are introduced by the optical system of the eye so as to improve resolution. In order to control the deformable mirror, light is shone into the eye, reflected from a point on the back surface and then passes through a lenslet array which provides light beams of known spatial orientation which are then detected and their position relative to a reference grid determined. The deformable mirror is moved by the processing system so as to compensate for the distortions or aberrations introduced by the optics of the eye, as measured against the reference grid, to improve resolution. While current technology provides general details of the retina for clinical diagnosis of retinal diseases, resolution is still limited.
Improving resolution of images obtained by a fundus camera, and which compensate for distortions or aberrations introduced by the optics of the eye is extremely important when attempting to diagnose retinal diseases such as retinopathy and glaucoma. The earlier diagnosis of glaucoma is particular important because glaucoma is a disease in which the retina deteriorates as a result, for example, of increased pressure within the eye. The effects of glaucoma are not noticed by the sufferer until the disease had become irreversible. Current techniques use optical field testing and fundus cameras to detect glaucoma after damage has already occurred.
If resolution of fundus cameras can be improved, the possibility exists that images with detail not currently possible, including structures such as rods and cones of the fundus, currently not visible without dissection, can be obtained. The ability to obtain such images will greatly improve diagnosis of retinal diseases and early treatment.